In the automotive repair industry, Evaporative Emission Control System (EVAP) leaks are difficult to diagnose using on board computer diagnostic tools as the reported error codes cannot directly identify what kind of EVAP leak is present. This requires the use of further diagnostic tools and techniques to determine the details of the reported error codes. Further time consuming methods are required to evaluate if any fixes made have properly fixed the car's EVAP system.
Modern day cars' EVAP system run self-tests during standard operation. These same tests are used by the car's internal systems to produce the previously mentioned error codes. During these tests the system pulls a vacuum or performs a pressure test on the fuel system. A leak is determined to be present if the airflow recorded by the internal test exceeds the expected amount. When a leak is found this causes the check engine light to illuminate and saves an error code. The saved error codes remain present on the car's computer and do not specify what kind of leak is present.
Once a leak error code is found, there are a number of methods and devices available to locate an EVAP leak and determine what kind of leak it is. An example of such a device is an EVAP smoke machine. This device produces smoke that fills the entire system with smoke. If there are any leaks, smoke will begin to leak out of the openings. This allows the automotive technician to then fix any found leak. This process is repeated until smoke cannot be seen coming out of the EVAP system.
This procedure can be very labor intensive and requires the vehicle being diagnosed to be stationary in a controlled environment. The automotive technician diagnosing the error codes could spend a great deal of time searching for the leak. While doing this he is decreasing the efficiency of the automotive repair shop as a whole as the vehicle being diagnosed is taking up diagnostic space in the automotive repair shop.
Once all of the leaks are successfully found and the automotive technician has fixed the issues, there is no immediate way for the automotive technician to check to see if the EVAP system is operating properly. One way to check the work done on the EVAP system is to check the car's computer with the diagnostic tools. Unfortunately, as the system monitor does not pass the EVAP system until a number of drive cycles have been completed, the automotive technician must take the car out for a test drive. This single test drive might not even be enough to validate his repair on the EVAP system as there is no standardized method shared between all types of automobiles. If the monitor does not pass the EVAP system the automotive technician must begin the process of diagnosing the car again. This can take many trips and waste valuable time and space solving this issue. The inefficiencies in diagnosing and checking performed work when testing for car EVAP system leaks calls for an alternative solution to be developed.
One proposed solution is to take advantage of EVAP system self-tests that any modern car runs during operation. A secondary device can be used to record data during the self-tests that would allow for immediate checking of work and quick determination if EVAP leaks exist.
Even though it is mandated that modern cars possess EVAP detection modules and testing procedures that occur during standard operation, the info needed to diagnose specific EVAP leak issues is lacking. The EVAP test itself tests to see if a vacuum can be held by the fuel tank for some amount of time. These self-tests can determine if a leak is present but not what kind of leak. Moreover, once a leak is determined to exist, working to ensure the maintenance done has properly repaired the EVAP system is a time consuming task. The reason this task is time consuming is that the system monitor will not pass the EVAP system until the automotive technician has repeatedly test driven the vehicle. This system monitor also does have a defined standard as to how to ensure the EVAP system has passed. The required testing can vary from a few test drives in one day to a number of test drives along with the vehicle being left overnight for a few days.
As the method to validate repair work done to an automobile's EVAP system mentioned above is both time consuming and unpredictable, the proposed device acts a solution to this problem. The device allows for the automotive technician to immediately recognize if the automobile's EVAP system is capable of holding a vacuum through the means of a pressure sensor recording gas tank pressures through a pressure transfer tube found in the gas cap vehicle interface.